Hierve el Agua in September

October through April gives you the sweet spot — dry weather, clear skies, and comfortable temperatures. December and January can actually get chilly up here, especially early morning and late afternoon, but the midday sun warms things up perfectly for swimming. Avoid May through September if possible. The rainy season turns the access road into a muddy mess, and afternoon thunderstorms can roll in fast. Plus, the pools get murky when it rains. Within the good months, aim for weekdays if you can swing it. Weekends bring crowds from Oaxaca City and Mexico City. Early morning visits (arrive by 9 AM) give you the best light for photos and smaller crowds. The golden hour before sunset is magical too, but you'll need to time your exit carefully since they lock the gates at 5 PM.